JP2010042542A - Printer and printing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To appropriately suppress an influence of an ambient temperature or a change thereof with respect to a printer which performs printing by using ultraviolet curing type ink that is cured by irradiation with ultraviolet rays. <P>SOLUTION: This invention relates to the printer 10 which performs printing by using the ultraviolet curing type ink that is cured by the irradiation with the ultraviolet rays, and includes an inkjet head 12 that is a printing head configured to eject a droplet of the ink to a medium 50, a heater 24 that is a medium heating means configured to heat the medium 50, and a UVLED 102 configured to irradiate the ink on the medium 50 with the ultraviolet rays. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a printing apparatus and a printing method.

2. Description of the Related Art Conventionally, printing apparatuses that use ultraviolet curable ink are known (see, for example, Patent Document 1). In such a printing apparatus, for example, UV irradiation is performed by UV irradiation means provided integrally with the inkjet head. As the ultraviolet light source, for example, UVLED is used.
JP 2004-358769 A

  Unlike ultraviolet lamps that irradiate ultraviolet rays together with visible light and infrared light, UVLEDs generate light only in the ultraviolet region. Therefore, when UVLED is used as an ultraviolet light source, no extra heat is generated and ultraviolet light can be irradiated with high energy efficiency. Further, the medium is not affected by heat.

  Therefore, the inventor of the present application has conducted intensive research on a configuration using UVLEDs. And when using UVLED as an ultraviolet light source, it discovered that a problem might generate | occur | produce because UVLED does not generate | occur | produce heat. For example, when a UVLED is used, the cured film of the medium or ink is not heated even if the UVLED emits light. Therefore, in this case, it has been found that the reaction rate of ink curing (polymerization) is likely to be dependent on the environmental temperature and its change. It has also been found that depending on the environmental temperature, the printing speed can be affected by the dependence of the reaction rate on the environmental temperature. Accordingly, an object of the present invention is to provide a printing apparatus and a printing method that can solve the above-described problems.

In order to solve the above problems, the present invention has the following configuration.
(Configuration 1) A printing apparatus that performs printing using ultraviolet curable ink that is cured by irradiation with ultraviolet rays, the print head ejecting ink droplets of ink onto the medium, and medium heating for heating the medium Means and a UV LED for irradiating the ink on the medium with ultraviolet light. The UVLED is, for example, a light emitting diode module that generates ultraviolet rays.

  If comprised in this way, when using UVLED which does not become a heat source as a light source of an ultraviolet-ray, for example, the medium and the cured film of an ink can be heated appropriately. Thereby, for example, curing of the ultraviolet curable ink can be appropriately promoted. Further, for example, a change in curability due to a difference in environmental temperature can be appropriately suppressed. Therefore, if comprised in this way, the influence of environmental temperature and its change can be suppressed appropriately.

  In addition, the ink can be cured stably by suppressing the influence of environmental temperature or the like and appropriately curing the ink. Thereby, for example, when printing is performed by the multi-pass method, it is possible to appropriately suppress the generation of stripes for each pass. In addition, for example, by curing the ink in a heated environment, the ink can be appropriately cured with a small dot diameter. Moreover, the film strength after curing can be appropriately improved, and for example, the curability and the glossiness can be appropriately improved. Furthermore, by improving the curability, for example, it is possible to appropriately improve the scratching performance and the like. Further, unlike the case of using an ultraviolet lamp or the like that generates heat, it is possible to perform heating with appropriately controlled temperature, and thus it is possible to appropriately prevent the medium from receiving heat damage such as thermal deformation. .

  As the medium heating means, it is preferable to use a platen heater that heats the platen that holds the print medium. Further, if necessary, a preheater for heating the medium before printing and an after heater for heating the medium after printing may be used in combination. As the heating method, methods such as radiant heating, heat conduction heating, and microwave heating can be used as appropriate. For example, when heating the print head in addition to the medium heating means, the medium heating means preferably heats the medium to a temperature between, for example, room temperature and the heating temperature of the print head.

  (Configuration 2) The medium heating means heats the medium to 35 ° C. or higher. If comprised in this way, the cured film of a medium and an ink can be heated to suitable temperature, for example.

  (Configuration 3) The heating means is provided at a position facing the print head across the medium. If comprised in this way, the cured film of a medium and an ink can be efficiently heated appropriately, for example.

  (Configuration 4) A printing method in which printing is performed using ultraviolet curable ink that is cured by irradiation of ultraviolet rays, wherein the medium is heated, ink droplets of the ink are ejected onto the medium, and the UV LED Irradiate the ink with UV rays. In this way, for example, the same effect as that of Configuration 1 can be obtained.

  ADVANTAGE OF THE INVENTION According to this invention, the influence of environmental temperature etc. can be suppressed appropriately in the printing apparatus which prints using the ultraviolet curing ink which hardens | cures by irradiation of an ultraviolet-ray, for example. Furthermore, by improving the curability, for example, the rubbing performance can be improved. Furthermore, for example, the glossiness of the image can be increased and a high-quality image can be obtained.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. FIG. 1 shows an example of the configuration of a printing apparatus 10 according to an embodiment of the present invention. FIG. 1A is a top view of the printing apparatus 10. FIG. 1B is a side view of the ultraviolet irradiation unit 20 in the printing apparatus 10 and shows the ultraviolet irradiation unit 20 viewed from the downstream side in the conveyance direction of the medium 50 together with the inkjet head 12. FIG. 3C shows a modified example of the configuration of the ultraviolet irradiation unit 20 together with the inkjet head 12.

  The printing apparatus 10 is an inkjet printing apparatus (inkjet printer) that performs printing using ultraviolet curable ink that is cured by ultraviolet irradiation. In this example, the printing apparatus 10 is a vertical inkjet printer that performs printing while conveying the medium 50, and includes a control unit 22, an inkjet head 12, a guide rail 18, a platen 14, a preheater 16, and an ultraviolet irradiation unit 20. And a heater 24. Although not shown, the printing apparatus 10 further includes, for example, a roller that conveys the medium 50. In the modification of the present embodiment, the printing apparatus 10 may be, for example, a flat bed type ink jet printer. In this case, the printing apparatus 10 appropriately includes, for example, a configuration necessary for a flat bed type inkjet printer, instead of the configuration unique to the vertical type inkjet printer.

  The control unit 22 is, for example, a CPU of the printing apparatus 10 and controls the operation of each unit of the printing apparatus 10. The inkjet head 12 is a print head that ejects ink droplets onto the medium 50. In this example, the inkjet head 12 ejects ink droplets onto the medium 50 while moving in the main scanning direction (Y direction) along the guide rail 18.

  The inkjet head 12 has a nozzle row in which a plurality of nozzles are arranged in the sub-scanning direction (X direction) orthogonal to the main scanning direction, and ejects ink droplets from each nozzle of the nozzle row. The inkjet head 12 may have a plurality of nozzle rows arranged in the Y direction, for example. For example, when the printing apparatus 10 is a printing apparatus that performs color printing, the printing apparatus 10 may include a plurality of inkjet heads 12. The printing apparatus 10 may include an inkjet head 12 corresponding to, for example, 4 to 8 colors or more.

  The guide rail 18 is a rail that guides the movement of the inkjet head 12 and the ultraviolet irradiation unit 20 in the main scanning direction, and scans the inkjet head 12 and the ultraviolet irradiation unit 20 in the main scanning direction. The platen 14 is a table that supports the medium 50 on which ink droplets land, and faces the inkjet head 12 with the medium 50 interposed therebetween.

  The preheater 16 is a heating mechanism that preheats the medium 50. In this example, as the preheater 16, known heating means such as a radiant heater, a heat conduction heater, and a microwave heater can be widely used.

  The ultraviolet irradiation unit 20 is a light source unit that irradiates the medium 50 on which ink droplets have landed with ultraviolet rays. In this example, the printing apparatus 10 includes a plurality of ultraviolet irradiation units 20. The plurality of ultraviolet irradiation units 20 are provided integrally with the inkjet head 12 so as to sandwich the inkjet head 12 in the main scanning direction.

  Each ultraviolet irradiation unit 20 includes a UVLED 102 that is a light emitting diode module that generates ultraviolet rays, and irradiates the ink on the medium 50 with ultraviolet rays. With this configuration, the ultraviolet irradiation unit 20 cures the ink that has landed on the medium 50. With this configuration, for example, when printing is performed while reciprocating the inkjet head 12 in the main scanning direction, it is possible to appropriately irradiate ultraviolet rays in each of the forward path and the backward path. This also makes it possible to appropriately perform a printing operation using ultraviolet curable ink.

  Furthermore, as necessary, for example, as illustrated in FIG. 1C, the ultraviolet irradiation unit 20 may include a condensing optical system 104. In this case, the ultraviolet irradiation unit 20 irradiates the ink on the medium 50 with ultraviolet rays via the condensing optical system 104. The condensing optical system 104 is an optical system having, for example, a lens, and condenses light from the UVLED 102. The condensing optical system 104 may include, for example, a plurality of lenses, and may include, for example, a prism.

  In addition, each ultraviolet irradiation part 20 may have several UVLED102, for example. In this case, for example, the plurality of UVLEDs 102 are arranged in the X direction in the ultraviolet irradiation unit 20 and constitute a UVLED array. The ultraviolet irradiation unit 20 may have a plurality of UVLED rows.

  Moreover, the position where the ultraviolet irradiation part 20 is provided may be a position different from the above, for example. For example, the ultraviolet irradiation unit 20 may be provided on the downstream side of the inkjet head 12 in the conveyance direction of the medium 50. In this case, for example, the ultraviolet irradiation unit 20 moves in the main scanning direction independently of the inkjet head 12 along a guide rail for the ultraviolet irradiation unit 20 provided in parallel with the guide rail 18. Even in such a configuration, the ink on the medium 50 can be appropriately irradiated with ultraviolet rays. This also makes it possible to appropriately perform a printing operation using ultraviolet curable ink.

  The heater 24 is an example of a medium heating unit that heats the medium. In this example, the heater 24 is a platen heater, is provided at a position facing the inkjet head 12 with the medium 50 interposed therebetween, and heats the medium 50 on the platen 14 to 35 ° C. or higher. As the medium heating means, a heat conduction heater, a microwave heating heater, a radiation heater, or the like can be used.

  The temperature of the heated medium 50 is, for example, 35 ° C. or higher, preferably 45 ° C. or higher. If comprised in this way, an ink can be hardened appropriately, suppressing the influence of environmental temperature etc. appropriately, for example. For example, considering the heat resistance of the medium 50, the temperature of the medium 50 is preferably set to 60 ° C. or less, for example, at the highest temperature. Therefore, the temperature of the medium 50 is, for example, 35-60 ° C, preferably 45-60 ° C.

  If comprised as mentioned above, also when using UVLED102 which does not become a heat source as an ultraviolet light source, the medium 50 and the cured film of an ink can be heated to appropriate temperature. Thereby, for example, curing (polymerization) of the ultraviolet curable ink can be appropriately promoted. Further, for example, a change in curability due to a difference in environmental temperature can be appropriately suppressed. Therefore, according to this example, it is possible to appropriately suppress the influence of the environmental temperature and its change.

  In addition, the ink can be cured stably by suppressing the influence of environmental temperature or the like and appropriately curing the ink. Thereby, for example, when printing is performed by the multi-pass method, it is possible to appropriately suppress the generation of stripes for each pass. In addition, for example, by curing the ink in a heated environment, the ink can be appropriately cured with a small dot diameter. Moreover, the film strength after curing can be appropriately improved, and for example, the curability and the glossiness can be appropriately improved. Furthermore, by improving the curability, for example, it is possible to appropriately improve the scratching performance and the like. Further, unlike the case of using an ultraviolet lamp or the like that generates heat, it is possible to perform heating while appropriately controlling the temperature, and thus appropriately preventing the medium 50 from receiving thermal damage such as thermal deformation. it can.

Hereinafter, the present invention will be described in more detail by way of examples.
Example 1
The printing apparatus 10 having the configuration described with reference to FIG. 1 was used to perform printing according to Example 1 using a known ultraviolet curable ink (for example, a UV curable ink manufactured by Mimaki) as the ink. Further, in Example 1, 3M IJ180-10 was used as the medium 50.

  In Example 1, the set temperature of the heater 24 was 40 ° C. As a result, the temperature of the medium 50 is 37 ° C. immediately above the heater 24. As the print settings (printing conditions), a first setting with a resolution of 600 dpi and 8 passes (8 passes) and a second setting with a resolution of 1200 dpi and 8 passes (8 passes) were used. Then, according to the first setting, a ramen pattern, which is a vertical and horizontal grid-like test pattern, was printed. Also, solid printing (printing with 100% solid) was performed with the black ink (K ink) at the maximum density according to the second setting.

(Example 2)
Printing according to Example 2 was performed in the same manner as Example 1 except that the set temperature of the heater 24 was set to 50 ° C. In this case, the medium 50 was 45 ° C. immediately above the heater 24.

(Comparative Example 1)
Printing according to Comparative Example 1 was performed in the same manner as in Example 1 except that heating by the heater 24 was not performed. In this case, the temperature of the medium 50 was room temperature (25 ° C.).

(Evaluation)
The following evaluations were performed on the printing results according to Examples 1 and 2 and Comparative Example 1. FIG. 2 is a diagram showing evaluation results for Examples 1 and 2 and Comparative Example 1. First, the dot diameter of the ink after curing was measured for the result printed with the first setting.

  FIG. 2A is a photograph showing the dot diameters of Examples 1 and 2 and Comparative Example 1. FIG. As a result of the measurement, the average dot diameter was 108 μm in Example 1, 106 μm in Example 2, and 113 μm in Comparative Example 1.

  From this result, it can be seen that in Examples 1 and 2 in which the medium 50 was heated, the dot diameter of the ink after curing was smaller than in Comparative Example 1 in which the heating was not performed. Moreover, in Example 2 heated to a higher temperature, it can be seen that the dot diameter is smaller. Further, in order to confirm the difference in the cured state of the ink, a JIS K5400 tape peeling test was further performed on the result of printing using the black ink (K ink) according to the first setting. As a result, in Comparative Example 1, peeling was observed on the surface of the ink coating. On the other hand, in Examples 1 and 2, no peeling was observed.

  From these results, it is considered that, for example, immediately after the ink has landed on the medium 50, the ink curability is different depending on the temperature under the ultraviolet irradiation unit 20. Further, it is considered that the curability of the ink is improved when heated to a high temperature.

  The difference in ink curability is, for example, the rubbing performance by an alcohol resistance (Alcohol durability) test in which an aqueous ethanol solution adjusted to various concentrations is used to rub the printed image to obtain the maximum ethanol concentration that does not cause image degradation. It can also be confirmed by evaluation. Even when such a test is performed, for example, by raising the temperature of the heating, it is possible to confirm that the rubbing performance is improved because the image does not deteriorate even when rubbing with a higher concentration of ethanol. .

  Next, the glossiness of the result printed with the second setting was evaluated. The glossiness was measured in each of the scan direction (Y direction) of the inkjet head 12 and the feed direction (X direction) that is the conveyance direction of the medium 50.

  FIG. 2B is a graph showing the evaluation result of glossiness. As can be seen from the graph, in both the scan direction and the feed direction, the glossiness is improved in Examples 1 and 2 in which the medium 50 is heated compared to Comparative Example 1 in which the heating is not performed. I understand that. Moreover, in Example 2 heated to higher temperature, it turns out that the glossiness is improving more.

  FIG. 3 is a diagram for explaining the glossiness in more detail. FIG. 3A is an SEM photograph of the surface (printed surface) of the medium 50 after printing. As can be seen from the photograph, in Examples 1 and 2, the unevenness in the feed direction is smaller than that in Comparative Example 1. Further, in Example 2 heated to a higher temperature, the unevenness in the feed direction is smaller than that in Example 1.

  Thus, it is considered that the fact that the unevenness in the feed direction is reduced and the smoothness of the print surface is improved affects not only the feed direction but also the glossiness in the scan direction. Therefore, as a reason why the glossiness is further improved by heating at a higher temperature, for example, the influence of such unevenness in the feed direction is considered to be smaller.

  Here, the reason why the smoothness of the print surface is improved by heating at a higher temperature will be considered. FIG. 3B is a diagram illustrating an example of the reason why the smoothness is improved by heating.

  When printing by the multi-pass method, the inkjet head 12 causes the next ink to land on the medium 50 so as to partially overlap the ink that has landed on the medium 50 in the previous scan operation. Therefore, an ink layer in which a plurality of layers of ink overlap is formed on the medium 50.

  In this case, for example, when the temperature of the medium 50 is high as in the first and second embodiments, the ink dropped immediately after the ink layer landed during the previous scan tends to spread before being cured by ultraviolet rays. It is thought that there is. As a result, it is considered that the surface of the printing surface becomes smooth.

  On the other hand, when the temperature of the medium 50 is low as in the first comparative example, for example, curing by ultraviolet rays occurs before the ink dropped immediately after the ink layer landed at the time of the previous scan is not sufficiently spread. It is thought that. As a result, the surface of the printing surface is considered to be uneven with respect to the feed direction.

  Such smoothness of the printing surface is obtained, for example, in a situation where an ink layer in which a plurality of layers of ink are overlapped is formed. On the ink layer, the wettability of the ink is usually higher than the direct surface of the medium 50. For this reason, for example, there are cases in which the ink bleeding method is variously different from the case where ink is directly landed on the medium 50.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above embodiment. It is apparent from the description of the scope of claims that embodiments with such changes or improvements can be included in the technical scope of the present invention.

  The present invention can be suitably used for a printing apparatus, for example.

1 is a diagram illustrating an example of a configuration of a printing apparatus 10 according to an embodiment of the present invention. FIG. 1A is a top view of the printing apparatus 10. FIG. 1B is a side view of the ultraviolet irradiation unit 20 in the printing apparatus 10. FIG. 3C shows a modified example of the configuration of the ultraviolet irradiation unit 20 together with the inkjet head 12. It is a figure which shows the evaluation result with respect to Examples 1, 2 and Comparative Example 1. FIG. 2A is a photograph showing the dot diameters of Examples 1 and 2 and Comparative Example 1. FIG. FIG. 2B is a graph showing the evaluation result of glossiness. It is a figure explaining a glossiness in more detail. FIG. 3A is an SEM photograph of the surface (printed surface) of the medium 50 after printing. FIG. 3B is a diagram illustrating an example of the reason why the smoothness is improved by heating.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Printing apparatus, 12 ... Inkjet head (printing head), 14 ... Platen, 16 ... Preheater, 18 ... Guide rail, 20 ... Ultraviolet irradiation part, 22 ... Control Part, 24 ... heater (medium heating means), 50 ... medium, 102 ... UVLED, 104 ... condensing optical system

Claims (4)

A printing apparatus that performs printing using ultraviolet curable ink that is cured by irradiation with ultraviolet rays,
A print head that ejects ink droplets of the ink onto the medium;
Medium heating means for heating the medium;
A printing apparatus comprising: a UVLED that irradiates the ink on the medium with ultraviolet rays.   The printing apparatus according to claim 1, wherein the medium heating unit heats the medium to 35 ° C. or more.   The printing apparatus according to claim 1, wherein the heating unit is provided at a position facing the print head across the medium. A printing method that performs printing using ultraviolet curable ink that is cured by irradiation with ultraviolet rays,
Warm the medium,
Discharging ink droplets of the ink onto the medium;
A printing method comprising irradiating the ink on the medium with ultraviolet rays by UVLED.